Field of the Invention
This disclosure relates to an imprint apparatus configured to detect a contact state between a mold used for imprinting and an imprint material supplied onto a substrate, an imprint method, and a device manufacturing method.
Description of the Related Art
An imprint technique is a technique for transferring a pattern formed on a mold to an imprint material supplied onto a substrate, and is proposed as one of lithography techniques for manufacturing semiconductor devices or magnetic storage medium. An imprint apparatus is configured to bring an imprint material (for example, a photo-curing resin) on a substrate and a mold into contact with each other and let the imprint material to cure in a contact state. The distance between the cured imprint material and the mold is increased and the mold is separated from the imprint material, so that the mold pattern is transferred to the imprint material on the substrate.
Air bubbles may remain in a concave of the mold pattern coming into contact with the imprint material. If the imprint material is cured with the air bubbles remaining in the concave, the imprint material is molded into a shape different from the shape of the concave. Therefore, a desired pattern is not formed on the substrate. Therefore, in order to facilitate filling of the imprint material into the concave of the pattern, a method of curving (deforming) a pattern surface of the mold so as to project toward the substrate and bringing the curved projection into contact with the imprint material is known (PCT Japanese Translation Patent Publication No. 2009-536591). By bringing the mold pattern into contact with the imprint material from a center portion of the pattern toward the outside, the imprint material may be filled easily in the concave of the pattern of the mold and probability of remaining of air bubbles may be reduced.
It is known that a contact state when the mold and the imprint material (or the substrate) come into contact with each other has an impact on the result of pattern transfer. The contact state includes posture (inclination) of the mold, and presence or absence of dust between the mold and the substrate. The mold and the imprint material preferably come into contact with each other so that a contact portion between the mold and the imprint material spreads out from a center toward a peripheral portion of the pattern in a concentric fashion. Therefore, a technique of observing the contact state between the mold and the imprint material is required. PCT Japanese translation Patent Publication No. 2006-514428 proposes a method of figuring out a contact state between a mold and the imprint material by observing how a plurality of individual liquid droplets (beads) supplied onto the substrate spread when the mold and imprint material come into contact with each other.
Many imprint materials used in the imprint technique have low viscosities. The liquid droplets of the imprint material supplied on the substrate spread over the substrate and join each other, so that a layer of the imprint material is formed on the substrate. Therefore, actually, how the individual liquid droplets of the imprint material spread over cannot be detected when the mold and the imprint material come into contact with each other.